Diseases of the cardiovascular system affect millions of people each year. A particularly prevalent form of cardiovascular disease is a reduction in the blood supply leading to the heart caused by atherosclerosis or other conditions that create a restriction in blood flow at a critical point in the cardiovascular system that supplies blood to the heart. In many cases, such a blockage or restriction in the blood flow leading to the heart is treated by a surgical procedure known as a Coronary Artery Bypass Graft (CABG) procedure, which is more commonly known as a "heart bypass" operation. In the CABG procedure, the surgeon "bypasses" the obstruction in, for example, a target coronary artery to restore normal blood flow to the heart by attaching an available source vessel to the obstructed coronary artery or by removing a portion of a vein or artery from another part of the body to use as a graft, and by installing the graft at points between the source vessel and the target artery to restore normal blood flow.
Although the CABG procedure has become common, the procedure itself is lengthy and traumatic and can damage the heart, the cardiovascular system, the central nervous system, and the blood supply itself. In a conventional CABG procedure, the surgeon must cut through the entire length of the sternum (a sternotomy), perform several other procedures necessary to attach the patient to a heart-lung bypass machine, clamp the aorta to stop the blood flow to the coronary arteries and infuse cardioplegia to stop the heart from beating in order to complete the bypass grafts.
In recent years, surgeons have begun performing CABG procedures using surgical techniques especially developed so that the CABG procedure can be performed while the heart is still beating. In such procedures, there is no need for any form of cardiopulmonary bypass, no need to perform the extensive surgical procedures necessary to connect the patient to a cardiopulmonary bypass machine, and no need to stop the heart. As a result, the "beating heart" surgery is much less invasive and the entire procedure can typically be achieved through a small number, typically one or two, comparatively small incisions in the chest.
As noted above, the CABG procedure requires that a fluid connection for restoring the flow of blood be established between two points to "bypass" a diseased or obstructed area to restore blood flow to the heart. Typically, a source vessel, such as a source artery with an unobstructed blood flow, for example, the left internal mammary artery (LIMA), or a bypass-graft having one end sewn to an unobstructed blood source such as the aorta, is anatomosed or sewn to a target occluded coronary artery, such as the left anterior descending (LAD) artery or other vessel, that provides blood flow to the muscles of the heart. Because the beating-heart CABG procedure is performed while the heart muscle is continuing to contract and pump blood, the anastomosis procedure is difficult to perform because the heart continues to move while the surgeons is sewing the anastomosis. However, it is important that the anastomosis be performed as rapidly as possible because the blood flow through the target coronary artery may be temporarily interrupted or reduced to avoid excessive blood loss. Also, the working space and visual access are limited because the surgeon may be working through a small incision in the chest or may be viewing the procedure on a video monitor if the site of the surgery is viewed via a surgical scope.
Accordingly, it is highly desirable to provide a surgeon with surgical instruments and techniques which allow either the sternotomy, or particularly the beating heart surgery, to be performed more rapidly and with as little trauma as possible to the patient. In addition, it is advantageous to provide the surgeon with compact surgical instruments, particularly in minimally invasive surgical procedures such as the beating heart procedures of previous mention, where the space within a surgical opening is very restricted. In a median sternotomy procedure where the chest is opened and a relatively large surgical opening is provided, the need for compact instruments may not be critical. However, compact surgical instruments which also enhance the efficiency of a surgical procedure, while improving upon the space which is available to a surgeon for viewing the surgical site as well as for accommodating the surgeon's hands, are advantageous and of value to the surgeon.
In a surgical procedure for constructing an anastomosis in which the LIMA is sewn to the LAD, it is necessary to pinch-off, or occlude, the LAD proximal to the anastomosic site to substantially reduce or eliminate the flow of blood therein. Typically, a surgeon occludes the artery by threading a silastic suture around the artery once or twice and tightening the suture in selected manner to compress and thus choke the artery until the flow of blood ceases. In another technique and associated occluder device for occluding an artery, a silastic suture is threaded through a choker tube, around the artery and back through the tube. A surgeon occludes the artery by gently pulling on the ends of the suture while pushing the choker tube towards the artery until blood flow ceases, and then clamping the tube walls against the suture via forceps, for example, to secure the occluder device in place. In these procedures, it is difficult to control the degree of tightness when applying the suture, which may result in trauma to the LAD. Further, the silastic suture, once secured, is only capable of applying a continuous preselected compression to the vessel. In addition, it is difficult to remove the tightened silastic suture which generally is embedded in the epicardium as well as in the surrounding tissue.
Other occluder configurations presently are available wherein the occluder is attached to, and thus is an adjunct part of, a stabilizer apparatus which is employed, for example, in a beating heart surgical procedure to maintain the surgical opening, that is, the thoracotomy. Examples of the stabilizer and occluder combination, as well as of such stabilizers alone, are disclosed in a copending U.S. patent application Ser. No. 08/603,758 filed on Feb. 20, 1996 and U.S. patent application Ser. No. 08/789,751 filed on Jan. 27, 1997, both entitled Surgical Instruments and Procedures for Stabilizing the Beating Heart During Coronary Artery Bypass Graft Surgery, which are incorporated herein by reference.